Don't waste your energy in memorizing things, rather utilize it in understanding things. You have the potential same as everyone else, but you use it the wrong way.

Pareto's Principle - The 80-20 rule, says that almost 80% of the output comes from 20% of our efforts. If you memorize the formulae, you will only be able to solve formulae-based questions, which is 20% of the output. But understanding the concept will eventually help you to solve concept-based as well as formulae-based questions, ultimately an 80% output from just investing 20%!!